New to this. In this Investopedia article on Delta the following looks like a typo -
How Do Options Traders Use Delta? Delta is used by options traders in several ways. First, it tells them their directional risk, in terms of how much an option's price will change as the underlying price changes. It can also be used as a hedge ratio to become delta-neutral. For instance, if an options trader buys 10 XYZ calls, each with a +0.40 delta. they would sell 4,000 shares of stock to have a net delta of zero. If they instead bought 10 puts with a -0.30 delta, they would buy 3,000 shares.
Let's take the first example. If $\Delta = +0.4$, then the total delta on the 10 XYZ calls is $\Delta \times 10 = + 0.4 \times 10 = + 4$, whereas the other leg has total delta $- 4,000$(?) Since for every $\\\$1$ that the XYZ stock goes up, the change in value of the second leg is $-$$\\\$4,000$. Is the intention here that each call contract on XYZ stock offers the holder the option to buy 1,000 shares of the stock? Even that would be strange, because the typical contract offers the holder the option to buy 100 shares of the underlying, as I understand it.